Heat generating devices, such as power semiconductor devices, may be coupled to a heat spreader to remove heat and lower the maximum operating temperature of the heat generating device. In some applications, coolant fluid may be used to receive heat generated by the heat generating device by convective thermal transfer, and remove such heat from the heat generating device. For example, jet impingement may be used to cool a heat generating device by directing impingement jets of coolant fluid onto the heat generating device or onto a target surface that is thermally coupled to the heat generating device.
Two-phase cooling may also be utilized, where the heat generating device is cooled by the phase change of the coolant fluid from a liquid to a vapor. In two-phase cooling, the transfer of heat from the device surface to the coolant fluid takes place via bubble generation from boiling. The use of the boiling phenomena to dissipate high heat fluxes (W/cm2) from surfaces is an effective mode of heat transfer. Every surface has a representative boiling curve that ranges from low heat flux (single phase) to maximum heat flux (i.e., safe heat flux) for a given fluid inlet temperature of a coolant fluid. Beyond the maximum heat flux value, all of the liquid coolant fluid transforms to vapor and may result in failure of the device that is attached to the two-phase cooling device.
Accordingly, a need exists for cooling apparatuses wherein the maximum heat flux for a given surface is increased.